Drugs of abuse gain control over behavior by usurping the activity of brain reward circuits. Thus, identifying behaviorally significant adaptations in these circuits is crucial for understanding the etiology and progression of alcohol addiction. Our preclinical research identified CaMKII?-AMPAR signaling as a novel target of moderate alcohol intake that also regulates the positive reinforcing effects of the drug in mice. This indicates that alcohol misappropriates molecular mechanisms of neuroplasticity within brain reward circuits. We propose that this maladaptive activity represents a molecular gateway from use to abuse, suggesting that the initial hit to this pathway is exacerbated during the development of dependence. We also showed that CaMKII signaling in the amygdala vs. mPFC differentially regulates alcohol self-administration. Since CaMKII is prominent in glutamate projection neurons, this suggests that excitatory efferents from these brain regions differentially regulate alcohol reinforcement. In this MERIT extension, we propose to move the field forward by testing the overall hypothesis that excitatory CaMKII?-positive corticolimbic circuits serve as functional units in the regulation of alcohol self-administration in a manner that is exacerbated by dependence. First, we will take a multidisciplinary approach to characterize the effects of initial alcohol use on activity of CaMKII?-dependent glutamate circuits (amygdala-to-accumbens and cortex-to-accumbens) and determine if alcohol-induced changes are exacerbated by dependence. These innovative discovery-based studies will inform subsequent goals of the project and move the field forward in our understanding of how alcohol dependence altered brain reward pathway function. Second, we will conduct mechanistic studies using optogenetic and pharmacological strategies to test the hypothesis that these neural circuits differentially regulate alcohol self-administraion during initial use and dependence. Overall, these innovative mechanistic studies will identify specific nuclei and circuits in which increased glutamate signaling contributes to escalated alcohol use in dependence; thus, identifying and validating novel mechanisms of a critical behavioral pathology that pervades the development and progression of alcohol addiction. RELEVANCE (See instructions): Alcohol addiction is a complex neuropsychiatric disorder that contributes to serious physical, psychiatric, and social problems. Evidence indicates that alcohol causes maladaptive changes in brain regions, and neural circuits, that regulate the fundamental process of reward. The goal of this research is to increase understanding of how alcohol alters these critical brain and behavioral processes during initial use and how these changes carry forward in dependence.